Passive seat belt systems commonly include a seat belt which is moved between an operative and an inoperative position by means of an electric motor drive in response for example to the closing and opening of an adjacent vehicle door. One end of the belt may thus be fastened to a carriage which is reversibly moved along a track by the electric motor. The belt may be withdrawn from a retractor against a spring bias and such retractors commonly incorporate a latching mechanism which prevents belt withdrawal when a predetermined condition is sensed, typically one or both of belt or vehicle, and thus retractor, acceleration in excess of certain limits. Many vehicle acceleration sansitive latching mechanisms are capable of latching when the vehicle is parked on a steep hill and this condition prevents movement of the belt of a passive system where this movement requires belt withdrawal from the retractor, with possible consequential damage by overheating to the electric motor which has to be energized to effect this movement. Such damage could of course occur in any kind of passive system where a drive motor was unable to move the seat belt, for any reason.
It is therefore an object of the present invention to provide means for avoiding damage to the drive motor of a passive seat belt system in the event of an obstruction to belt movement.
It is also an object of the invention to provide means responsive to drive motor overload to initiate protective procedures for the system.
It is a further object of the invention to provide means for proper functioning of a passive seat belt system including a retractor regardless of undesired latching thereof against belt withdrawal.
It is also an object of the invention to provide a seat belt retractor capable of signalling whether or not it is latched against belt withdrawal.
It is also an object of the invention to provide a seat belt retractor having a latch mechanism capable of being disabled in response to an electrical signal.
It is also an object of the invention to provide a seat belt retractor capable of signalling the quantity of the seat belt retained therein or withdrawn therefrom.